Researchers at Kings College Hospital, South London, and the Royal Shrewsbury Hospital are studying the connection between pfos and migraines.

Divers are far more likely than other members of the public to discover that they have a pfo because they are likely to suffer from decompression illness* as a result. Divers are also more likely to pursue a surgical operation to close the heart defect in order to carry on diving. This makes divers a great source of study material for the heart researchers, and the investigation is largely based upon the experiences of divers.

The connection between pfos and certain types of migraine has long been established. Diving doctor Dr Peter Wilmshurst has warned that people who have post-dive migraine with aura - a pronounced visual disturbance - are likely to be suffering from a large pfo.

The type of migraine that is particularly important is migraine with aura. The aura is usually a visual disturbance which can have a number of forms such as a shimmering blind spot or geometric patterns, zig-zag lines, etc.
Sometimes the aura includes abnormal sensation in part of the body (often half the body -i.e. right or left side) or weakness down one side. Typically the aura precedes the headache, but they can come on around the same time or the aura can occur without headache.
It has been know since 1944 that individuals with migraine with aura (M with A) have an increased risk of having decompression illness (DCI) but the reason was not known until it was shown that both M with A and DCI are associated with a large PFO. Dr Peter Wilmshurst told Divernet.

The current study follows up on those divers who had surgery to close their pfo, and investigates whether any who had suffered from migraine beforehand have experienced symptoms after the surgery.

Current research suggests that the pfo treatment appears to resolve migraine symptoms in post-operation divers.

The implications of the research could be far-reaching, as up to one in ten people suffer from migraines - though only a small minority of these will suffer severe symptoms such as migraine with aura.

Fixing a pfo involves a relatively minor surgical procedure. A small device is inserted through a vein in the leg and worked up into the heart; the device is then manoeuvered into the pfo, and a wire mesh umbrella deployed either side of the hole. Heart tissue should then grow onto the mesh surface.

* Bubbles formed in the bloodstream during a dive are routinely filtered out in the lungs after blood returns to the right hand side of the heart. A hole in the heart wall which allows blood to pass through to the left hand side of the heart can, potentially, also allow the passage of bubbles. Bubbles in the arterial blood are more likely to become lodged in body tissues, including the brain and spine, and can result in decompression illness. Fuller explanation here

Wilmshurst, Bryson et al:
Lancet 1989 (Vol 2, pages 1302-6)
Clinical Science 2000 (Vol 99, pages 65-75)
Clinical Science 2001 (Vol 100, pages 539-420)

Wilmshurst, Bryson et al:
Lancet 2000 (Vol 356, pages 1648-51)
Clinical Science 2001 (Vol 100, pages 215-220)

Related links
New research quantifies risk of hole in the heart in divers
Hole in the heart a very common cause of bends for divers
Aberdeen Hyperbaric Chamber decompression information and PFOs

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